The present invention generally relates to micro-electro-mechanical devices, and more particularly to a micro-electro-mechanical device having a moveable mass which is supported and moved by a flexure having an integrally formed actuator.
Micro-electro-mechanical systems (hereinafter xe2x80x9cMEMSxe2x80x9d) are integrated systems of small size where the feature sizes are generally of micron dimensions. MEMS devices are created on a common silicon substrate utilizing microfabrication technology like that used for integrated circuit (IC) processing. The fabrication processes selectively etch away parts of the silicon wafer or add new structural layers to form the mechanical and electromechanical devices.
One unique feature of MEMS is the extent to which actuation, sensing, control, manipulation, and computation are integrated into the same system. Examples of MEMS devices include individually controlled micro-mirrors used in a projection display, accelerometers that sense a crash condition and activate airbags in cars, pressure sensors, xe2x80x9clab on a chipxe2x80x9d systems, and data storage devices.
Many MEMS devices include masses that are moveable within the system. In these MEMS devices, beams or flexures are often used to support the moveable masses in the system. The beams supply both support of the system""s mass and compliance for the system""s mass movements. If motion of the system""s mass must be limited, additional features are generally created in the system to limit the motion as desired. The actual movement of a system""s mass is accomplished by yet another device separate from the beams or flexures and motion limiting features. Referred to herein generically as actuators or micro-actuators, various types of devices may be used to cause movement of a system""s mass. Micro-actuators which are used in MEMS devices use a variety of methods to achieve actuation: electrostatic, magnetic, piezoelectric, hydraulic and thermal.
In MEMS devices such as those mentioned above, space limitations of the device must be considered. Even though MEMS devices are by definition already extremely small, it may be desired to maximize the size of one component of the device relative to the size of another component or to the size of the entire device. Thus, it would be desirable to reduce the space occupied by such other components of the device, or to eliminate selected components entirely. In addition, it would be desirable to reduce the number of process steps needed to fabricate a particular MEMS device or specific components of a MEMS device. As noted above, MEMS devices are manufactured using micro-fabrication technology like that used in the production of integrated circuits. A reduction or simplification of the process steps required to form a particular MEMS device or one of its components would speed the manufacturing process, and reduce the likelihood of error in the manufacturing process.
In the example of MEMS devices having masses that are moveable within the system, it is often the moveable mass whose size is desired to be maximized with respect to the total size of the device. For example, in a data storage device, the moveable mass may be or include the storage medium. To maximize the data storage capacity of the device, it would be desirable to make the moveable mass as large as possible within the confines of the device. In such devices, it would be desirable to reduce the total space occupied by the flexures supporting the moveable mass, the features limiting the mass motion, and the actuator that moves the mass.
A micro-electro-mechanical device comprises a moveable mass, a frame for supporting the mass, and a flexure extending between the mass and the frame. The flexure includes an integral actuator for moving the mass with respect to the frame.